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1. Field of the Invention
The invention relates generally to the field of computer networking devices. More particularly, the invention relates to a flexible, policy-based mechanism for managing, monitoring, and prioritizing traffic within a network and allocating bandwidth to achieve true Quality of Service (QoS).
2. Description of the Related Art
Network traffic today is more diverse and bandwidth-intensive than ever before. Today""s intranets are expected to support interactive multimedia, full-motion video, rich graphic images and digital photography. Expectations about the quality and timely presentation of information received from networks is higher than ever. Increased network speed and bandwidth alone will not satisfy the high demands of today""s intranets.
The Internet Engineering Task Force (IETF) is working on a draft standard for the Resource Reservation Protocol (RSVP), an Internet Protocol-(IP) based protocol that allows end-stations, such as desktop computers, to request and reserve resources within and across networks. Essentially, RSVP is an end-to-end protocol that defines a means of communicating the desired Quality of Service between routers. RSVP is receiver initiated. The end-station that is receiving the data stream communicates its requirements to an adjacent router and those requirements are passed back to all intervening routers between the receiving end-station and the source of the data stream and finally to the source of the data stream itself. Therefore, it should be apparent that RSVP must be implemented across the whole network. That is, both end-stations (e.g., the source and destination of the data stream) and every router in between should be RSVP compliant in order to accommodate the receiving end-station""s request.
While RSVP allows applications to obtain some degree of guaranteed performance, it is a first-come, first-served protocol, which means if there are no other controls within the network, an application using RSVP may reserve and consume resources that could be needed or more effectively utilized by some other mission-critical application. A further limitation of this approach to resource allocation is the fact that end-stations and routers must be altered to be RSVP compliant. Finally, RSVP lacks adequate policy mechanisms for allowing differentiation between various traffic flows. It should be appreciated that without a policy system in place, the network manager loses control.
Recent attempts to facilitate traffic differentiation and prioritization include draft standards specified by the Institute of Electrical and Electronics Engineers (IEEE). The IEEE 802.1Q draft standard provides a packet format for an application to specify which Virtual Local Area Network (VLAN) a packet belongs to and the priority of the packet. The IEEE 802.1p committee provides a guideline to classify traffic based on a priority indicator in an 802.1Q frame tag. This allows VLANs to be grouped into eight different traffic classes or priorities. The IEEE 802.1p committee does not, however, define the mechanism to service these traffic classes.
What is needed is a way to provide true Quality of Service (xe2x80x9cQoSxe2x80x9d) in a network employing a non-deterministic access protocol, such as an Ethernet network, that not only has the ability to prioritize and service different traffic classes, but additionally provides bandwidth management and guarantees a quantifiable measure of service for packets associated with a particular traffic class. More specifically, with respect to bandwidth management, it is desirable to employ a weighted fair queuing delivery schedule which shares available bandwidth so that high priority traffic is usually sent first, but low priority traffic is still guaranteed an acceptable minimum bandwidth allocation. Also, it is desirable to centralize the control over bandwidth allocation and traffic priority to allow for QoS without having to upgrade or alter end-stations and existing routers as is typically required by end-to-end protocol solutions. Further, it would be advantageous to put the control in the hands of network managers by performing bandwidth allocation and traffic prioritization based upon a set of manager-defined administrative policies. Finally, since there are many levels of control a network manager may elect to administer, it is desirable to provide a variety of scheduling mechanisms based upon a core set of QoS profile attributes.
A flexible, policy-based, mechanism for managing, monitoring, and prioritizing traffic within a network and allocating bandwidth to achieve true Quality of Service (QoS) is described. According to one aspect of the present invention, a method is provided for managing bandwidth allocation in a network that employs a non-determninistic access protocol. A packet forwarding device receives information indicative of a set of traffic groups. The packet forwarding device additionally receives parameters, such as bandwidth and priority parameters, corresponding to the traffic groups. After receiving a packet associated with one of the traffic groups on a first port, the packet forwarding device schedules the packet for transmission from a second port based upon parameters corresponding to the traffic group with which the packet is associated. Advantageously, in this manner, a weighted fair queuing schedule that shares bandwidth according to some set of rules may be achieved.
According to another aspect of the present invention, a method is provided for managing bandwidth allocation and traffic prioritization in a packet forwarding device. The packet forwarding device receives information indicative of a set of traic groups. The packet forwarding device additionally receives information defining a Quality of Service (QoS) policy for the traffic groups. After a packet is received by the packet forwarding device, a traffic group with which the packet is associated is identified. Subsequently, rather than relying on an end-to-end signaling protocol for scheduling, the packet is scheduled for transmission based upon the QoS policy for the identified traffic group. Therefore, bandwidth allocation and traffic prioritization are based upon a set of administrative policies over which the network manager retains control.
According to yet another aspect of the present invention, a number of QoS queues are provided at each port of the packet forwarding device. A current bandwidth metric is determined for each of the QoS queues for a particular port. The QoS queues are divided into two groups based upon their respective bandwidth metrics and their respective minimum bandwidth requirements. Subsequently, the groups are used as a first level arbitration mechanism to select a QoS queue that will source the next packet.
Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follows.